The Miss Thistlebottoms of the world are always going on about dangling participles,1 but few usage experts mention dangling infinitives.2 What’s a dangling infinitive? It’s an infinitive, “to” + verb, that is not correctly attached to the agent (a noun or pronoun) that carries out the action specified by the verb. When a sentence starts with an infinitive phrase, the subject of the main clause should be the agent that carries out the action specified by the infinitive:
To prepare an NMR sample, we dissolved the crystals in CDCl3.
Here the pronoun “we” carries out the action specified by the infinitive “to prepare.” Infinitive constructions also work correctly when the subject is implied, as in an imperative sentence:
To prepare an NMR sample, [you] dissolve the crystals in CDCl3.
where the implied subject pronoun “you” is doing the preparing.
In scientific writing, however, we tend to use passive voice, especially in the experimental section of a paper; and the use of the passive eliminates the agent that is needed to carry out the action in the infinitive:
To prepare an NMR sample, the crystals were dissolved in CDCl3.
Now we have a problem: “crystals” is the subject of the main clause, but crystals do not prepare NMR samples.